1. The Field of the Invention
The present invention relates to orthopedic splinting materials and methods utilizing an open-celled foam sheet impregnated with a water curable resin. The present invention further relates to the use of such resin-impregnated foam materials as walking heels or laminates between casts and walking heels, as supports for orthotic devices, such as arch supports for foot orthotics, and as protective coverings for animal hoofs.
2. The Prior Art
Severe injury to body limbs, particularly injuries involving a fresh fracture of the bone or damage to the soft tissue supporting the bone, are frequently treated by temporarily immobilizing the injured limb with a splint until the time swelling has abated. After such time, the splint may then be removed and a rigid cast applied. Because a temporary splint must allow for swelling of the limb, the splint generally should not encompass the entire limb so as to better accommodate expansion of the limb. Many different systems have been devised for providing orthopedic splints.
For example, U.S. Pat. Nos. 2,759,475 and 2,800,129 disclose blanks for forming splints comprising a solid thermoplastic material provided on one surface with a foam plastic layer. The blank is heated to a temperature such that the solid thermoplastic material becomes soft, and is then applied to the body part and shaped to form the splint.
Similarly, U.S. Pat. No. 4,442,833 discloses a casting or splinting bandage comprising a closed-cell polymer foam and a plurality of sheets of a textile material impregnated with a water curable resin.
U.S. Pat. No. 4,235,228 discloses an orthopedic material comprising a plaster impregnated fabric core, a layer of padding around at least one surface of the fabric, and a length of tubular stockinet encircling the fabric and padding. This combination can be cut to a desired length, dipped in water to begin hardening of the plaster, attached to a patient by a bandage or other fastener, and allowed to harden to form a splint.
The systems described in U.S. Pat. Nos. 4,442,833 and 4,235,228 are relatively damp when applied, and can thus provide undesirable environments for any wounds present and/or promote skin maceration on those body parts over which the splints are applied.
U.S. Pat. No. 3,985,128 discloses a splint that can be applied dry, but ultraviolet light is required to harden the splint. Thus, such a splint can only be used where a source of ultraviolet light is available. U.S. Pat. No. 3,728,206 describes a foam impregnated with a thermoplastic resin.
U.S. Pat. No. 4,411,262 discloses a constructional material comprising a flexible substrate impregnated or coated with a resin system which is cured by air moisture. In one embodiment, the flexible substrate may be a foam which is resin impregnated by solvent coating onto the foam an isocyanate sump residue which has a viscosity between 3,000 and 50,000 centipoise.
U.S. Pat. No. 4,628,917, which issued on Dec. 16, 1986 and which is assigned to the same assignee as the present invention, discloses a combination of materials that can be used to form a splint or protective covering, including a support mat comprising a flexible fabric impregnated with a water curable resin with a water restricting film along at least one of its major surfaces, and a pressure sensitive adhesive coated padding that can be adhered to the support mat after the fabric is exposed to water so that the resultant laminate can be applied to a person with the dry surface of the padding against the person's skin.
In selecting suitable materials for forming orthopedic splints, the prior art has encountered several problems. First, it has been sought to use a low viscosity resin which may be easily coated upon the supporting fabric or material to be used in the splint. However, splints prepared from such low viscosity resins, when formulated to give a proper set time, typically result in unacceptably high exotherms, which can result in burning the patient. High viscosity resins, on the other hand, typically require complicated techniques for application, such as solvent coating the resin onto the fabric or substrate. Further, the fabrics or scrim materials used in such splints have typically been relatively inextensible in order to provide sufficient strength for the resulting splint; however, the result is a splinting material which has poor extensibility and which thus does not conform well to the body part to which it is applied. Finally, if the splinting materials used in the prior art do not exhibit sufficient water vapor permeability, skin maceration can result.
From the foregoing, it will be appreciated that what is needed in the art is improved orthopedic splinting materials which have acceptable setting times and exotherms without the need for complicated resin application techniques, and which avoid the problems of the prior art set forth above. Such splinting materials and methods for applying such splinting materials are disclosed herein.
Further, in the prior art technologies involving walking heels for casts, foot orthotics, and protective coverings for animal hoofs, problems have arisen due to the irregularities of the surfaces involved. Ideally, it would be desirable to provide a material that would result in an even walking surface for each of these applications, regardless of the irregularity of the surface to which the material is attached. Advantageously, the resin-impregnated foam materials of the present invention serve exceptionally well in these other applications.